JPH0228503Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to an improvement of an aperture device for a camera that is built into a camera such as a cine camera or a video camera and that automatically adjusts the amount of light for photographing.

[Prior art and problems]

The camera diaphragm device previously disclosed in Japanese Patent Laid-Open No. 58-80627 by the applicant of the present application forms an aperture 5a centered on the optical axis 0-0', as shown in FIGS. 1 and 2. The outer wall 7c and the inner wall 7b of the yoke 7 face each other along the edge of the opening 5a of the base 5 to the blade actuating member 4 which opens and closes the blade member 2 whose base end 2c is supported on the base 5 and which forms an aperture aperture. permanent magnet 1
0 is fixed, electric coils 12a and 12b are housed in the gap between the permanent magnet 10 and the outer wall 7c, respectively, and are supported by a bearing member in a direction perpendicular to the optical axis 0-0' and oscillate in the optical axis 0-0' direction. The movement of the freely movable movable member 12 is transmitted to the blade actuating member 4 by a transmission member 12g to perform aperture control.

However, in general, magnetic flux has the characteristic of forming a magnetic loop such that it exits from the north pole face of a permanent magnet and returns to the south pole face through the shortest distance to minimize magnetic resistance, as shown in Figure 3. The magnetic field generated between the permanent magnet 10a and the outer wall 7c of the yoke 7 is influenced by the bottom 7f of the yoke 7, and the magnetic flux in the vicinity forms a magnetic loop that does not reach the outer wall 7c but passes directly through the bottom 7f. The magnetic flux density B in the vicinity of the bottom 7f becomes sparse compared to the surrounding area, making it impossible to form a uniform magnetic field as shown in FIG. As shown in FIG. 5, the combined rotational force generated in the movable member 12a and 12b has a characteristic that it becomes significantly smaller at both end portions of the open side and the closed side, and as a result, uneven rotation occurs in the movable member 12. The problem was that smooth operation was not possible due to the unevenness of rotation.

[Purpose of invention]

The present invention was developed in view of the above-mentioned drawbacks, and it is an object of the present invention to provide an aperture device for a camera that can uniformize the rotational force generated in the movable member and perform smooth aperture control.

[Summary of the idea]

In order to achieve the above object, the camera diaphragm device of the present invention has a drive device that controls the opening and closing of the diaphragm blades that are disposed in the optical axis aperture provided on the base and can be freely opened and closed, as will be described later. , a movable member that is rotatably supported in the optical axis direction on a base around the optical axis aperture and has coils at left and right apexes different from the shaft bearings, and a movable member that faces the coil and is on the base. It consists of a magnet provided around the shaft opening, and a yoke that faces the magnet via the coil and forms a magnetic loop with the magnet, and the distance between the yoke and the magnet is varied in the optical axis direction. By narrowing the moving coil so that the magnetic flux density acting on the coil increases as it approaches the base side, the composite torque of the driving torque acting on the left and right coils of the movable member is approximately equal, and the movable member The rotational force generated in the member is made to be approximately uniform.

[Example of idea]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail based on the embodiments shown in FIGS. 6 to 11 of the accompanying drawings.

The diaphragm device of the present invention is constructed by integrally incorporating the diaphragm section and the drive section into a base.

In Fig. 6, the base is a plate-shaped or cylindrical material with an aperture 5a centered on the optical axis 0-0', and is usually configured in a circular shape according to the lens barrel of the camera. It is incorporated like this.
An annular groove 5b is formed in the outer circumferential surface of the opening 5a in the base, and a ring-shaped blade actuating member 4 is fitted into the annular groove 5b so as to be swingable, and the blade actuating member 4 is supported from above. A plate 3 is fixed to the base with screws.

Therefore, the blade actuating member 4 is held between the base plate and the support plate 3 and is slidable in the direction of the arrow γ in FIG. Further, pins 4b corresponding to the number of aperture blades to be described later are implanted in the blade operating member 4, and these pins 4b are designed to penetrate through slits 3b formed in the support plate 3. 4b is a slit 3 that is formed as the blade actuating member 4 slides back and forth.
It is possible to move within b.

Aperture blades 2 usually have 2, 3, 5, 6, or 8 blades.
The base end 2c of each blade is supported by a pin 3a implanted in the support plate 3, and each blade 2 is connected to the support plate 3.
It can freely rotate around the base end 2c along the top,
Its tip 2d faces the optical axis opening 5a of the base.

At the same time, each blade 2 is connected to the pin 4 of the blade operating member 4.
b is engaged with the cam groove 2b, and as the blade operating member 4 slides, the tip of the blade 2 rotates around the base end 2c, and the aperture aperture can be adjusted arbitrarily around the optical axis 0-0'. It is beginning to form.

The blades 2 placed on the support plate 3 are held by a presser plate 1, and the presser plate 1 is fixed to the base with screws 6. The presser plate 1 has a hole 1b into which the pin 3a is fitted and a slit 1b into which the pin 4b is fitted.
are engaged with each other.

4c in the figure is a stopper pin, and the blade operating member 4
The diaphragm blades 2 may be rotated by a certain angle between the fully open position and the closed position, but in order to restrict the movement stroke, the diaphragm blades 2 are fitted into slits 3c formed in the support plate 3.

In the illustrated example, a support plate 3 is provided separately from the base to hold the aperture blades 2, but in this case, a wide flange is formed on the base, and the blades 2 are attached to this flange.
may be supported, and in this case there is no need to provide the support plate 3.

In addition, although the illustration shows the case where the aperture blade 2 is composed of three blades, one blade, two blades, five blades, six blades, eight blades, etc.
The same applies to the case where the number of sheets is set or the number of sheets is other than that. Furthermore, the blade actuating member 4 can be omitted by directly connecting the aperture blade 2 to a drive section to be described later.

Next, the driving section will be explained.

The movable member 12 is composed of an electric coil in which a conducting wire is wound around the optical axis 0-0', and the outer diameter of the coil is formed into a ring shape having a major diameter part _l1 and a minor diameter part _l2 ,
A pair of support shafts 12c, 1 are provided at opposing positions of this short diameter portion _l2 .
2d are respectively provided to protrude outward.

These support shafts 12c and 12d are synthetic resin mounting seats 1.
2e, and the mounting seat 12e is adhesively fixed to the movable member 12.

Bearing members 13 and 14 that rotatably support the support shafts 12c and 12d are integrally attached to the base plate with screws, and a bent piece 7 of the yoke 7 is provided.
d and 7e.

Further, this movable member 12 and the aforementioned blade actuating member 4 are connected through driving transmission members 12f, 12g, and 4d.

That is, as shown in FIG. 7, a transmission pin 12f is protruded from the mounting seat 12e of the shafts 12c and 12d provided on the movable member 12, and a lever 12g with one end engaged with the transmission pin 12f is moved from the bearing member 12. ,14
The pin 1 formed at the other end of the lever 12g is swingably attached to the mounting bent pieces 7d and 7e.
2h is fitted into the engagement receiving portion 4d of the blade actuating member 4. In addition, since this fitting rotates in different planes of motion, the pin 12h of the lever 12g and the engagement receiving portion 4d of the blade actuating member 4 are constantly connected throughout the rotation range in order to suppress the play in the fitting as small as possible. The engagement receiving portion 4d has a curved surface or a sharp cross-sectional shape so as to form a point contact.

Therefore, the blade actuating member 4 is rotated in the γ direction shown by the arrow in FIG. 6 via the transmission pin 12f and the lever 12e, through which the movable member 12 swings up and down in FIG. 7 about the shafts 12c and 12d.

Next, the permanent magnet 10 is installed on a yoke 7 attached to a base, and the yoke 7 is made of iron or other soft magnetic material, and has an inner wall 7b and an outer wall 7c formed around the opening 7a of the optical axis 0-0'. A permanent magnet 1 is provided on the inner wall 7b side of this recess 8.
0 is fixed with adhesive. Also, this permanent magnet 10
As shown in an enlarged view in FIG. 8, the outer wall 7c facing the permanent magnet 10 is formed in an appropriate shape so that the distance to the permanent magnet 10 becomes narrower and the magnetic flux density increases as you go from the open side of the outer wall to the bottom 7f of the recessed part. It has been done.
Specifically, when the yoke width of the yoke 7 is T, and the yoke diameter at approximately the center of the yoke width T is L, the shape of the outer wall 7c is as follows:
The portion from the side to the center is formed with a yoke radius that is approximately half the yoke diameter L, and the portion from the center to the outer wall open side is formed with an inclination equal to the draft angle of the bottom press die.

In other words, the magnetic flux densities B ₁ and B ₂ occurring between the permanent magnets 10a and 10b and the outer wall 7c have the characteristics shown by the solid lines in FIG. By swinging the electric coils and magnetically cutting the magnetic flux, driving torques are generated in the respective electric coil portions 12a and 12b, and the movable member 12 is rotated by the rotational force F resulting from the combination of the driving torques. The rotational force F at that time becomes approximately uniform as shown in FIG.

Therefore, the movable member 12 swings smoothly in the direction of the arrow d about the support shafts 12c and 12d without uneven rotation, and the swinging motion of the movable member 12 is immediately transmitted through the motion transmission members of the transmission pin 12f and the lever 12g. The blade actuating member 4 is slid in the direction of the arrow γ shown in FIG. 6 to drive the aperture blades 2 in the closing direction to narrow down the aperture 5a and suppress the amount of light to an appropriate value. This aperture control operation is well-known. This is automatically performed by controlling the direction of the current flowing through the electric coil portions 12a, 12b of the movable member 12 according to changes in the amount of photographing light using a control circuit.

In the above embodiment, the shape of the ring-shaped movable member is not limited to the oval shape, and various shapes can be adopted, and the movable member can be permanently shaped as shown in FIG. Magnet 10a, 1
It may be integrally formed by a pair of left and right coils 12a' and 12b' wound around 0b.

Furthermore, although a pair of yokes and permanent magnets are provided facing each other, they may each be annular yokes and permanent magnets.

Furthermore, by adhesively fixing a permanent magnet onto the bottom 7f of the concave portion of the yoke, it is possible to remove either the inner wall or the outer wall.Also, if the permanent magnet is attached to the outer wall side, the inner wall can be attached to the inner wall as described in the above embodiment. It is sufficient to mold it into a shape that exhibits a magnetic flux density as shown in the figure.

[Effect of idea]

As is clear from the above explanation, according to the present invention, the distance between the yoke and the magnet is narrowed so that the magnetic flux density acting on the coil that swings in the optical axis direction increases as the coil approaches the base side. By that,
The combination of the driving torques acting on the left and right coils of the movable member is approximately equal, and by making the rotational force generated in the movable member approximately uniform, the movable member is driven smoothly without uneven rotation. The diaphragm blades can be driven to open and close by the swinging movement of the movable member, which has the effect of smoothly controlling the diaphragm.

[Brief explanation of the drawing]

1 to 5 explain the prior art, and FIG. 1 is a perspective view showing an overview of the aperture device, and FIG.
The figure is a schematic sectional view of the drive part, Figure 3 is a partially enlarged view of the drive part to explain the state of magnetic flux density, Figure 4 is a characteristic diagram of the magnetic flux density, and Figure 5 is a diagram of the rotational force generated in the movable member. It is a characteristic diagram showing a state. 6 to 11 show embodiments of the present invention. FIG. 6 is an exploded perspective view of the throttle device according to the invention, and FIG. 7 is an exploded perspective view of the drive member shown by the overall symbol in FIG. 6. Figure 8 is a schematic sectional view of the drive part, Figure 9a,
b is a characteristic diagram showing the magnetic flux density state of the magnetic field involved in the left and right coils of the movable member, and FIG. 10 is a characteristic diagram showing the state of the rotational force generated in the movable member.

Claims (1)

[Claims for Utility Model Registration] A driving device for controlling the opening and closing of aperture blades that are freely openable and closable in an optical axis aperture provided on a base, is swung in the optical axis direction on a base around the optical axis aperture. a movable member that is freely supported on its shaft and has coils at left and right apexes different from the shaft bearings; a magnet that faces the coil and is provided around the optical axis opening on the base; In an aperture device composed of a yoke that faces the magnet and forms a magnetic loop, the magnetic flux density acting on the coil that swings in the optical axis direction increases as the coil approaches the base. An aperture device for a camera, characterized in that the distance between the yoke and the magnet is narrowed.